Food allergies are on the rise with the highest rates of intolerance recorded among women and the Asian population, a study concludes.

Research into just how common these allergies are also records shellfish as the most commonly reported food followed by fruit and vegetables, dairy and peanuts.

Consistent with previous studies, the team point to higher rates of awareness and reporting as a possible explanation for the sex difference.

“Recent reports suggest that food allergies are on the rise, with more food-allergy related hospitalizations in the U.S. over the last decade,”​ said Dr Li Zhou, lead author and assistant professor at Brigham and Women's Hospital.

“However, many studies have been based on telephone surveys or have focused on a specific food allergen or allergen group." ​

Around 17 million Europeans suffer from food allergies, with 3.5 million of them less than 25 years of age, according to the European Academy of Allergy and Clinical Immunology (EAACI).

The academy also found 60% allergic patients are women, which they suggest was down to biological and psychological factors.

Study details​

Dr Zhou and her team began sifting through allergy data taken from 2.7 million patients between 2000 and 2013.

These subjects were categorised according to their sex, racial/ethnic group, and allergen group.

The prevalence of reactions that were potentially IgE-mediated and anaphylactic were also noted.

In total 97,482 patients (3.6%) with one or more food allergies or intolerances were identified.

The prevalence of food allergy and intolerance were found to be higher in females (4.2% vs 2.9%;) and Asians (4.3% vs 3.6%).

The most common food allergen groups were shellfish (0.9%), fruit or vegetable (0.7%), dairy (0.5%) and peanut (0.5%).

Of the 103,659 identified reactions to foods, 48.1% were potentially immunoglobulin-E (IgE)-mediated affecting 50.8% of food allergy or intolerance patients while 15.9% were anaphylactic.

Further tests performed on about 20% of patients with reported peanut allergy revealed that 57.3% had an IgE level of grade 3 or higher.

IgE and anaphylaxis​

Anaphylaxis is a rapid allergic reaction that can be characterised by an itchy rash, throat or tongue swelling, shortness of breath and lightheadedness.

Immunoglobulin E (IgE) is produced as part of an immune response to a food allergy. Doctors look out for allergen specific IgE as an indicator of the allergic response's severity.

Grade 3 is considered a ‘high’ level of allergen specific IgE antibody produced with doctors advised to consider the patient’s history and risk of severe reaction and/or anaphylaxis.

Differing food preparations​

“These findings support the pressing need for more food allergy evaluations, as well as a call for more allergists/immunologists, especially given new recommendations for early food introductions, less reliance on isolated positive test results to diagnose food allergy,”​ the study concluded.

In explaining their findings, the team did not discount the influence of genetic, cultural and environmental factors.

“The higher prevalence documented among Asians was similar to that in previous studies in Western nations,”​ the study commented, “but higher than that reported among Asian nations and Asian-born immigrants.”​

“This inconsistency may be partially attributable to the different preparation of peanuts; in Asian countries peanuts are primarily boiled whereas in Western countries they are roasted, a preparation that increases the allergenicity of the peanut.”​

The EAACI have reported similar patterns in the past. In continental Europe the most common food allergies are to fruit and vegetables.

In Anglo-Saxon countries hazelnuts, peanuts and walnuts are the most problematic.

Allergy to fish and shellfish prevails in Scandinavia and Northern Europe.